1. Field of the Invention
The present invention relates to an apparatus for microwave processing in a magnetic field such as for use in depositing or etching processes.
2. Description of the Prior Art
One example of known microwave processing apparatuses is an ion shower apparatus as described in Japanese Patent Application No.sho55-141729 (publication No.sho57-133636) in the name of Seitaroh Matsuo. The apparatus of this type is well known as an ECR (electron cyclotron resonance) apparatus which utilizes divergence of a magnetic field. FIG. 1 is a schematic cross sectional view of this type apparatus. The apparatus comprises a reaction chamber 33 provided with a plasma generating space 19, a coil 17 enclosing the space 19 and a substrate holder 13. The plasma generating space 19 is partially sectioned by means of a partition 31 having a center plasma outputting opening 32. The substrate holder 13 is located apart from the opening 32 by a predetermined distance 30 (20.about.30 cm) in which lines of magnetic force diverge toward the holder (region 29). When microwaves are inputted to the space 19 from a waveguide 34 through a quartz window 15, a plasma is generated in the space 19 and some of the plasma is drawn to the reaction chamber 33 through the opening 32 by virtue of the diverging magnetic field to shower the substrates 1 on the holder 13 with the plasma.
The pressure of the plasma is limited during the deposition up to 0.003 Torr at which ions have substantially large mean free paths. The microwave energy inputted to the apparatus is also limited up to 0.5 KW. In this prior art structure, however, a substantial portion of inputted microwave energy is lost during the treatment in the form of a plasma flow passing through the reaction chamber 33 and drawn by an evacuation system 10. This is particularly problematic when deposition is desired to coat a relatively large area, e.g. with diamond by chemical vapor deposition. Furthermore, the uniformity of the deposited films were not so high, i.e. the thicknesses of the deposited films at center positions and peripheral positions substantially differed.
The microwave processing has been employed also for plasma etching as proposed by the applicant (Patent Publication for Opposition No.sho63-44827 filed on Oct. 14, 1985). The effect of etching varies dependent upon the position by use of prior art processing apparatuses for the same reason as the thickness disparity described above. Namely, the accuracy of fine patterns becomes worse at peripheral positions and it is impossible to effect anisotropic etching in the direction normal to a substrate.